The study will investigate how visual information is represented in the prefrontal cortex, the brain area involved with higher cognitive functions, before and after learning to perform a cognitive task. Monkeys will be trained in cognitive tasks that require them to observe and remember visual stimuli. Neurophysiological recordings with an array of microelectrodes at various training stages will allow us to determine the patterns of neuronal activation and the functional interactions between neurons. The experiments will uncover the nature of changes that take place in the prefrontal cortex by learning to perform a cognitive task.